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A157007 Numbers k such that 2^k + 27 is prime. 6
1, 2, 4, 5, 8, 10, 13, 14, 16, 40, 41, 44, 86, 110, 125, 133, 134, 145, 154, 184, 194, 301, 308, 320, 685, 1001, 1066, 1496, 1633, 2005, 2864, 3241, 6286, 11585, 12854, 16514, 16540, 19246, 24538, 28705, 57644, 65366, 85276, 89113, 194854, 266680, 376790, 478088 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(49) > 5*10^5. - Robert Price, Nov 06 2015

LINKS

Table of n, a(n) for n=1..48.

Henri Lifchitz and Renaud Lifchitz, PRP Records, search for 2^n+27

EXAMPLE

For k = 1, 2^1 + 27 = 29.

For k = 2, 2^2 + 27 = 31.

For k = 4, 2^4 + 27 = 43.

MATHEMATICA

Delete[Union[Table[If[PrimeQ[2^n + 27], n, 0], {n, 1, 2000}]], 1]

Select[Range[5000], PrimeQ[2^#+27]&] (* Harvey P. Dale, Mar 24 2011 *)

PROG

(PARI) for(n=1, 1e3, if(isprime(2^n+3^3), print1(n", "))) \\ Altug Alkan, Oct 04 2015

(MAGMA) [n: n in [0..1000] | IsPrime(2^n+27)]; // Vincenzo Librandi, Oct 05 2015

CROSSREFS

Cf. A019434 (2^(2^n)+1), A057733 (2^n+3), A123250 (2^n+5).

Cf. A104071 (primes of the form 2^k+27).

Sequence in context: A115392 A342541 A179509 * A173509 A007729 A174868

Adjacent sequences:  A157004 A157005 A157006 * A157008 A157009 A157010

KEYWORD

nonn

AUTHOR

Edwin Dyke (ed.dyke(AT)btinternet.com), Feb 20 2009

EXTENSIONS

More terms from Harvey P. Dale, Mar 24 2011

a(33)-a(42) from Robert Price, Oct 04 2015

a(43)-a(47) discovered by Henri Lifchitz and Lelio R Paula from Lifchitz link by Robert Price, Oct 04 2015

a(48) from Robert Price, Nov 06 2015

STATUS

approved

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Last modified September 19 17:46 EDT 2021. Contains 347564 sequences. (Running on oeis4.)